Mode Switching Coordinated Control Strategy Of HEV Based On Robust Control Theory

Hybrid electric vehicle(HEV)has multiple working modes,and it switches between different modes.The torque fluctuation of the power system is easily caused during the switching process,resulting in unstable power transmission.Therefore,it is of great significance to study the coordinated control of HEV mode switching to improve the ride comfort and achieve fast and smooth switching.In this paper,the parallel hybrid electric vehicle(PHEV)is taken as the research object.Based on the modeling of the entire vehicle and various components,the switching process of the working mode is analyzed.The mode switching with the clutch engagement is divided into clutch slipping stage I,clutch slipping stage II,speed synchronization stage and torque coordination stage four phases,and a dynamic torque coordination control strategy is designed.Firstly,determine the structural model of PHEV system and design its mode switching rules.Building the Matlab/Simulink model for the single-shaft PHEV structure,taking the mode switching process from the pure electric mode switching to the engine driving mode as an example,the process is divided into four phases.The method for evaluating the effect of mode switching coordination control is given,for designing further control strategy and paving the way with simulation.Secondly,a mode switching coordination control strategy based on ?-synthesis theory is designed.The strategy uses engine speed tracking and motor torque compensation methods to design the robust controller for the engine and the motor during mode switching.Based on the ?-synthesis toolbox in Matlab,the designed controller and weighting function parameters are solved and simulated.The results show that the robust control strategy based on ?-synthesis can effectively compensate the engine torque following error through the motor torque,reducing the fluctuation of the total demand torque and the jok of the whole vehicle during the start of the engine,which ensures the smoothness of power transmission.Finally,mode switching coordination control strategy based on H-infinity theory is designed.The control strategy is based on the theory of switching systems and conducts in-depth studies on the dynamic coordination of engine,motor and clutch in PHEV mode switching process.PHEV mode switching process controller and switching rules with parameter uncertainty are designed,and the control strategy is simulated under the conditions of Matlab/Simulink and Advisor.The results show that under the control strategy of the H-infinity theory,the influence of parameter uncertainty on the engine torque is reduced,and the engine and motor speed is smoother,improving the smoothness of the PHEV mode switching process,and verifying the effectiveness of control strategy.